Undefined behaviour on shifts

[spth]

Compiling this with SDCC yields warnings:

minimp3.h:379: warning 116: left shifting more than size of object changed to zero
minimp3.h:649: warning 116: left shifting more than size of object changed to zero

Looking at the code, there is indeed a problem:

s = g_deq_L12[ba*3 - 6 + b % 3]*(1 << 21 >> b/3);
…
y *= g_expfrac[e & 3]*(1 << 30 >> (e >> 2));

1 is an int, so on targets where int is less than 31 bits, the 1 << 30 most likely does not do what is intended here. I think changing both 1 to 1l should fix the issue.